Glass frits

ABSTRACT

Glass frits, conductive inks and articles having conductive inks applied thereto are described. According to one or more embodiments, glass frits with no intentionally added lead comprise TeO 2  and one or more of Bi 2 O 3 , SiO 2  and combinations thereof. One embodiment of the glass frit includes B 2 O 3 , and can further include ZnO, Al 2 O 3  and/or combinations thereof. One embodiment provides for conductive inks which include a glass frit with no intentionally added lead and comprising TeO 2  and one or more of Bi 2 O 3 , SiO 2  and combinations thereof. Another embodiment includes articles with substrates such as semiconductors or glass sheets, having conductive inks disposed thereto, wherein the conductive ink includes glass frits having no intentionally added lead.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.12/022,294, filed Jan. 30, 2008, now U.S. Pat. No. 7,736,546, issuedJan. 15, 2010, which is incorporated herein by reference.

TECHNICAL FIELD

Embodiments of the invention relate to glass frits, conductive inksincluding a frit, and articles having such conductive inks appliedthereto.

BACKGROUND

Conductive inks, obscuration enamels and decorative enamels typicallyuse lead-based glass frits because they have a low melting range, lowmolten viscosity and stability against uncontrolled devitrification.Obscuration enamels are used in the automotive industry and conductiveinks are used in the electronics industry, including in the manufactureof solar cells or photovoltaic cells.

Photovoltaic (“PV”) cells convert sunlight into electricity by promotingcharge carriers in the valence band of a semi-conductor into theconduction band of the semiconductor. The interaction of photons in thesunlight and doped semiconductor materials form electron-hole paircharge carriers. These electron-hole pair charge carriers migrate in theelectric field generated by the p-n semiconductor junction and collectedby a conductive grid or metal contact printed or applied to the surfaceof the semiconductor, through which it flows to the external circuit.Crystalline silicon PV cells in today's industry are typically coatedwith an anti-reflective coating to promote light adsorption, whichincreases PV cells efficiency. However, the anti-reflective coatingimposes high electrical resistance to the charge carrier flowing fromthe semiconductor to the metal contact. Such anti-reflective coatingsoften comprise silicon nitride, titanium oxide or silicon oxide.

Conductive inks are used to form these conductive grids or metalcontacts. Conductive inks typically include a glass frit, a conductivespecies, such as silver particles, and an organic medium. To form themetal contacts, conductive inks are printed onto the substrate in apattern of grid lines or other pattern by screen printing or otherprocess. The substrate is then fired, during which electrical contact ismade between the grid lines and the substrate. This contact is enhancedby the formation of individual silver crystallites at theglass-substrate interface. Without being bound by theory, it is believedthat charge carriers are transferred from the substrate to the silvercrystallites and then transferred to the gridline either through theglass layer by tunneling or directly to the silver of the gridline, ifthere is direct contact of the crystallite with both the gridline andthe semiconductor. Lower firing temperatures are desirable in thisprocess because of the lower cost involved and energy saved.

As otherwise mentioned herein, the anti-reflective coating enhanceslight absorption but also acts as an insulator which impairs the excitedelectrons from flowing from the substrate to the metal contacts.Accordingly, the conductive ink should penetrate the anti-reflectivecoating to form metal contacts having ohmic contact with the substrate.To accomplish this, conductive inks incorporate glass frits to aid withsintering silver particles to a substrate and to promote adhesion andohmic contact between the formed metal contact and the substrate. Whenthe glass frit liquefies, it tends to flow toward the interface betweenthe silver particles and the anti-reflective coating on the substrate.The melted glass dissolves the anti-reflective coating materials as wellas some of the metal particles and substrate. Once the temperaturedecreases, the molten silver and the melted or dissolved substraterecrystallize through the liquid phase. As a result, some of the silvercrystallites are able to penetrate the antireflective layer and formohmic contact with the substrate. This process is referred to as“fire-through” and facilitates a low contact resistance formation and astronger bond between conductive grid or metal contact and thesubstrate.

The automotive, electronics and solar cell industries place greateremphasis on using environmentally-friendly components and processes.This emphasis has been further urged by the need to comply withenvironmental regulations. In response, the solar cell industry ismoving to eliminate the use of lead in components and materials used insolar panels of cells.

Accordingly, there is a need for a lead-free glass frit which can befired at a lower temperature and that can penetrate the anti-reflectivelayer and form metal contacts in ohmic contact with a substrate.

SUMMARY

Embodiments of the present invention relate to tellurium containingfrits having no intentionally added lead and the uses thereof. Accordingto one or more embodiments, the frits described herein have very lowviscosity and are particularly corrosive. For example, in one or moreembodiments, the frits tend to dissolve refractory materials typicallyused in PV applications as anti-reflective layers such as SiO₂, TiO₂ andSiN_(x).

Specific embodiments include a frit having no intentionally added leadwhich includes TeO₂ and Bi₂O₃ and/or SiO₂. As used throughout thisapplication, the terms “no intentionally added lead” and “substantiallylead-free” shall mean a frit having lead in an amount less than about1,000 ppm. In one or more embodiments, TeO₂ is present in an amountbetween about 0.01% by weight to about 10% by weight. Another embodimentalso includes B₂O₃. According to one embodiment, the frit also includesat least one first oxide component. A second embodiment of the inventionfurther includes at least one second oxide component, while a thirdembodiment includes at least one alkali metal oxide component. At leastone alkaline earth metal oxide is included in another embodiment of theinvention.

The first oxide component of one or more embodiments can include ZnOand/or Al₂O₃. ZnO is present in one embodiment in an amount of about 0%by weight to about 15% by weight, while the Al₂O₃ is present in anamount of about 0% by weight to about 3% by weight in anotherembodiment. The second oxide component of one embodiment includes Ag₂O,Sb₂O₃, GeO₂, In₂O₃, P₂O₅, V₂O₅, Nb₂O₅, and Ta₂O₅ and can be present inthe following amounts: Ag₂O, P₂O₅, V₂O₅, Nb₂O₅, and/or Ta₂O₅ are presentin an amount of about 0% by weight to about 8% by weight; In₂O₃ and/orSb₂O₃ are present in an amount in the range from about 0% by weight toabout 5% by weight; and GeO₂ is present in an amount in the range fromabout 0% by weight to about 10% by weight. Embodiments with at least onealkali metal oxide component utilize Na₂O, Li₂O, and/or K₂O in an amountin the range from about 0% by weight to about 3% by weight, whileembodiments with at least one alkaline earth metal oxide componentutilize BaO, CaO, MgO and/or SrO in an amount in the range from about 0%by weight to about 8% by weight.

In accordance with another aspect of the present invention, a conductiveink includes a substantially lead-free frit having TeO₂ and Bi₂O₃ and/orSiO₂, along with a conductive species, and no intentionally added lead.One or more embodiments of the conductive ink include TeO₂ in an amountin the range from about 0.01% by weight to about 10% by weight. Anotherembodiment utilizes silver as a conductive species. In accordance withone or more embodiments, the conductive ink includes frits which alsoincorporate B₂O₃. Further conductive ink embodiments can have a fritwhich includes at least one first oxide component, at least one secondoxide component, at least one alkali metal oxide component, and/or atleast one alkaline earth metal oxide component. According to oneembodiment, frit is present in the conductive ink in the amount in therange from about 1% by weight to about 5% by weight.

Another aspect of the invention includes an article comprising asubstrate, and a conductive ink as described herein disposed on thesubstrate. According to one or more embodiments, the substrate is asemiconductor, a glass sheet and/or an enamel disposed on a glass sheet.Embodiments with a semiconductor substrate also include ananti-reflective layer disposed on the substrate with the conductive inkis disposed on the anti-reflective layer. In a more specific embodiment,the anti-reflective layer includes SiO₂, TiO₂ or SiN_(x)

In one or more embodiments of the article, the conductive ink comprisesa substantially lead-free frit and a conductive species. In a specificembodiment, the frit includes B₂O₃ and TeO₂.

The foregoing has outlined rather broadly certain features and technicaladvantages of the present invention. It should be appreciated by thoseskilled in the art that the specific embodiments disclosed may bereadily utilized as a basis for modifying or designing other structuresor processes within the scope of the present invention. It should alsobe realized by those skilled in the art that such equivalentconstructions do not depart from the spirit and scope of the inventionas set forth in the appended claims.

DETAILED DESCRIPTION

Before describing several exemplary embodiments of the invention, it isto be understood that the invention is not limited to the details ofconstruction or process steps set forth in the following description.The invention is capable of other embodiments and of being practiced orbeing carried out in various ways.

Specific embodiments of the present invention include a frit having nointentionally added lead which includes TeO₂ and Bi₂O₃ and/or SiO₂. Inone or more embodiments, TeO₂ is present in an amount between about0.01% by weight to about 10% by weight. In a more specific embodiment,TeO₂ is present in an amount between about 0.5% by weight to about 5% byweight. In an even more specific embodiment, TeO₂ is present in anamount between about 0.5% by weight to about 2% by weight. In one ormore embodiments, Bi₂O₃ is present in the frit in an amount in the rangefrom about 40% by weight to about 95% by weight. In a specificembodiment, Bi₂O₃ is present in the range from about 50% by weight toabout 80% by weight, while an even more specific embodiment has Bi₂O₃ inthe range from about 60% by weight to about 75% by weight.

One or more embodiments of the frit include SiO₂ in an amount in therange from about 0% by weight to about 30% by weight. In specificembodiments, SiO₂ can be present in an amount in the range from about 1%by weight to about 4% by weight.

According to one or more embodiments, B₂O₃ is also included in the frit.In a specific embodiment, B₂O₃ is present in an amount in the range fromabout 0.1% by weight to about 10% by weight. In a more specificembodiment, B₂O₃ is present in an amount in the range from about 0.5% byweight to about 8% by weight. In an even more specific embodiment, B₂O₃is present in an amount in the range from about 1% by weight to about 4%by weight.

One embodiment of the present invention includes a frit having TeO₂,Bi₂O₃, SiO₂, and B₂O₃. Another example of a frit includes TeO₂, Bi₂O₃,SiO₂, B₂O₃, ZnO and Al₂O₃. An additional embodiment of a frit includes0.01% to 10% by weight of TeO₂, 40% to 95% by weight of Bi₂O₃, 0% to 30%by weight of SiO₂, 0.1% to 10% by weight of B₂O₃, 0% to 15% by weight ofZnO and 0% to 3% by weight of Al₂O₃. A further embodiment of the presentinvention includes a frit having TeO₂, Bi₂O₃, SiO₂, B₂O₃, ZnO and asecond oxide component. One or more embodiments substitute ZnO withAl₂O₃, while another embodiment incorporates both ZnO and Al₂O₃.

One embodiment of the invention includes at least a first oxidecomponent such as:

-   -   ZnO in an amount in the range from about 0% by weight to about        10% by weight; and/or    -   Al₂O₃ in an amount in the range from about 0% by weight to about        2% by weight.

Another embodiment of the invention incorporates at least one secondoxide component including:

-   -   Ag₂O in an amount in the range from about 0% by weight to about        4% by weight;    -   Sb₂O₃ in an amount in the range from about 0% by weight to about        4% by weight;    -   GeO₂ in an amount in the range from about 0% by weight to about        4% by weight;    -   In₂O₃ in an amount in the range from about 0% by weight to about        4% by weight;    -   P₂O₅ in an amount in the range from about 0% by weight to about        4% by weight;    -   V₂O₅ in an amount in the range from about 0% by weight to about        4% by weight;    -   Nb₂O₅ in an amount in the range from about 0% by weight to about        4% by weight; and/or    -   Ta₂O₅ in an amount in the range from about 0% by weight to about        4% by weight.

One or more embodiments of the present invention incorporate at leastone alkali metal oxide component including:

-   -   Na₂O in an amount in the range from about 0% by weight to about        2% by weight;    -   Li₂O in an amount in the range from about 0% by weight to about        2% by weight; and/or    -   K₂O in an amount in the range from about 0% by weight to about        2% by weight.

Additional embodiments of the invention also include at least onealkaline earth metal oxide component such as:

-   -   BaO in an amount in the range from about 0% by weight to about        4% by weight;    -   CaO in an amount in the range from about 0% by weight to about        2% by weight;    -   MgO in an amount in the range from about 0% by weigh to about 2%        by weight; and/or    -   SrO in an amount in the range from about 0% by weight to about        4% by weight.

One or more embodiments of the present invention include conductive inkswhich utilize the frits disclosed herein and a conductive species. Inone or more embodiments, the conductive ink utilizes a conductivespecies such as silver in powdered or particulate form. In one or moreembodiments, the silver particles can be spherical, flaked or amorphousor provided in a colloidal suspension. Other non-limiting examples ofsuitable conductive species include conductive metals such as gold,copper and platinum in powdered or particulate form.

The silver species used in one or more embodiments can be in the form offine powders of silver metal or silver alloys. In other embodiments,some of the silver can be added as silver oxide (Ag₂O), silver saltssuch as silver chloride (AgCl), silver nitrate (AgNO₃) and/or silveracetate.

Conductive inks according to one or more embodiments of the presentinvention also incorporate bismuth tellurate and/or bismuth silicatepowders. It has been found that the addition of bismuth tellurate and/orbismuth silicate powders can control crystallization of the glass fritby shifting the onset of crystallization to lower temperatures. Whilethe present invention should not be bound by theory, it is believed thatbismuth tellurate and/or bismuth silicate powders provide nucleationsites for crystal growth. In a photovoltaic application, the glass fritshould penetrate through or dissolve the anti-reflective layer to enablethe silver to form ohmic contact, however, controlling theaggressiveness of glass frit is desired to prevent it from penetratingthrough the junction of the semiconductor which would shunt the device.Other embodiments utilize other known phases which produce the same orsimilar effect as bismuth tellurate and/or bismuth silicate, such astitania, zirconia, phosphorous compound and others.

The conductive ink according to one or more embodiments may also includea liquid vehicle. It is believed that the liquid vehicle disperses theparticulate components and facilitates transfer of the ink compositiononto a surface. Specifically, the liquid vehicle, which, according toone or more embodiments, is composed of solvent(s) and dissolved organicresin(s), disperses the conductive species and frit to obtain an inkhaving suitable viscosity. In addition to influencing paste viscosity itis believed that the resin(s) improve the adhesion and green-strength ofthe paste after it has been deposited on the substrate and dried.Various liquid vehicles with or without thickening agents, stabilizingagents, surfactants, defoamers and/or other common additives aresuitable for use in the preparation of the embodiments of the presentinvention. Exemplary liquid vehicles which can be used include alcohols(including glycols), esters of such alcohols such as the acetates,propionates and phthalates, for instance dibutyl phthalate, terpenessuch as pine oil, terpineol and the like. More specific liquid vehiclesinclude diethylene glycol monbutyl ether, terpineol, isopropanol,tridecanol, water, and 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate.Some embodiments utilize vehicles that also contain volatile liquids topromote fast setting after application to the substrate.

Examples of suitable organic resins dissolved into the liquid vehicleinclude ethyl cellulose, methyl cellulose, nitrocellulose, ethylhydroxyl ethyl cellulose, carboxymethyl cellulose, hydroxylpropylcellulose and other cellulose derivatives. Other examples include resinssuch as acrylic acid esters, methacrylic acid esters, polyvinylalcohols, polyvinyl butyrals, polyesters and polyketones.

In one specific embodiment, solutions of resins such aspolymethacrylates of lower alcohols are used, while in a more specificembodiment, the liquid vehicle includes ethyl cellulose dissolved insolvents such as pine oil and monobutyl ether of diethylene glycol.

The ratio of liquid vehicle to solids in the conductive ink according toone or more embodiments can vary considerably and is determined by thefinal desired formulation viscosity which, in turn, is determined by theprinting requirements of the system. In one or more embodiments, theconductive ink can contain about 50 to about 95% by weight solids andabout 5 to about 50% by weight liquid vehicle.

One or more embodiments of the conductive inks may additionally comprisefurther additives known in the art, such as colorants and stainingagents, rheology modifiers, adhesion enhancers, sintering inhibitors,green-strength modifiers, surfactants and the like.

In one or more embodiments of the present invention, a preservative isincorporated into the coating composition. Some embodiments utilizepreservatives such as boric acid, phosphoric acid, hydrochloric acid,nitric acid, sulphuric acid and/or combinations thereof, while otherembodiments utilize other preservatives known in the art.

Another aspect of the present invention pertains to articles including asubstrate, and a conductive ink disposed on the substrate. One or moreembodiments include a conductive ink having a frit as described herein,that is, a frit comprising TeO₂ and having no intentionally added lead.Examples of substrates include semiconductor wafers, glass sheets andother suitable substrates used in the photovoltaic industry for theformation of photovoltaic cells. In one embodiment, the semiconductorsubstrate is doped with phosphorous, while another embodiment includesdoped conductive inks. According to one embodiment of the presentinvention, the semiconductor substrate comprises amorphous,multicrystalline or monocrystalline silicon.

In one or more embodiments, the semiconductor substrate has ananti-reflective coating disposed thereon and the conductive ink isprinted on top of the anti-reflective coating. The anti-reflectivecoating according to some embodiments comprises silicon dioxide,titanium oxide, silicon nitride or other coatings known in the art.

Methods known in the art can be used to produce semiconductor substrateshaving a conductive ink disposed thereon. One or more embodiments employcrystalline silicon such can be either amorphous, monocrystalline ormulticrystalline. Coatings may be applied to the substrates, and suchcoatings or layers can be produced according to known processes, such aschemical vapor deposition, plasma vapor deposition, and the like. Theanti-reflective coatings can also be applied using chemical vapordeposition techniques. In some embodiments, plasma enhanced chemicalvapor deposition techniques are used to dispose the anti-reflectivecoating on the substrate. Semiconductor articles, according to one ormore embodiments, may also be etched or textured to reduce reflection ofsunlight and enhance the level of light absorption. According to one ormore embodiments, the conductive ink is thereafter applied to thesurface of the substrate or anti-reflective coating by screen printingor other technique. The substrate is heated or fired to a temperature ofabout 750° to 850° C. to sinter the particles of the conductive ink intogridlines. As otherwise discussed in this application, the firingprocess allows the glass frit to melt and penetrate or dissolve theanti-reflective coating disposed on the substrate. In one or moreembodiments, the conductive species forms crystallites at the interfaceof the frit and substrate interface, which enhances electrical or ohmiccontact between the metal contacts formed from the conductive ink andthe semiconductor substrate.

One or more embodiments of the invention include glass sheet substrateswith conductive ink printed thereon. In a specific example, the glasssheet is an automotive backlite. In other examples, the glass sheet hasan enamel disposed thereon and a conductive ink is printed on theenamel. Enamels used in some embodiments may be obscuration enamelswhich provide protection from ultra-violet rays which can deterioratethe adhesive glues that bond the automotive windshields to a vehiclebody. Embodiments of glass sheet substrates may also include a pliableinterlayer usually made up of polyvinyl butyrate (“PVB”).

As with embodiments of the invention related to semiconductor articleswith conductive ink disposed thereon, the conductive ink can be appliedto the glass sheet substrate or enamel substrate by screen printing orother known method. In further embodiments, the substrates are firedheated or fired to a temperature of about 600° to 750° C. to sinter theparticles of the conductive ink into grid lines.

Without intending to limit the invention in any manner, embodiments ofthe present invention will be more fully described by the followingexamples.

EXAMPLES

Two inks (Ink A and Ink B) were prepared having at least a frit and aconductive species. Inks A and B were prepared using a generalprocedure. The general procedure includes batching and dispersing theexamples using triple roll milling. Alternative dispersion processesknown in the industry such as bead milling, sand milling and colloidmilling could also be used to disperse the solid particles in theorganic binder medium.

Inks A and B both had a frit content of 3% by weight and silver in anamount of 97% by weight (on a solids basis). Both frits were bismuthborosilicate compositions, had similar coefficients of thermal expansionand glass transition temperatures. Ink A contained a frit known in theart which had no intentionally added lead. Ink B contained a frit knownin the art which had no intentionally added lead and also incorporatedTeO₂.

Eight textured, monocrystalline silicon wafers with a 40 ohm/squarephosphorus doped emitter and boron doped base having a silicon nitrideanti reflective coating were used. The back surfaces of the eight waferswere printed with commercially available back surface aluminum ink andsilver rear contact ink. Both inks were thoroughly dried. Four waferswere then printed on the front surface with Ink A using a 325 meshscreen (Comparative Cells 1-4). Four additional wafers were printed onthe front surface with Ink B in an identical manner (Cells 5-8). The PVcells were then dried and fired in an infrared furnace to a peak firingtemperature as noted in Table 1. Each wafer was fired at the peaktemperature for approximately 3 to 5 seconds. After cooling, the partswere tested for their current-voltage (I-V) characteristics.

TABLE 1 COMPARISON OF ENAMEL LAYERS Comparative Comparative ComparativeComparative Cell 1 Cell 2 Cell 3 Cell 4 Fill Factor (FF) 0.467 0.5230.494 0.562 Efficiency (Eff) 9.8 11.4 10.8 12.3 Peak Firing 800° C. 820°C. 820° C. 820° C. Temp Cell 5 Cell 6 Cell 7 Cell 8 Fill Factor (FF)0.519 0.659 0.659 0.681 Efficiency (Eff) 11.2 14.3 14.3 14.8 Peak Firing800° C. 820° C. 820° C. 820° C. Temp

The “fill factor” and “efficiency” refer to measurements of theperformance of a semiconductor. The term “fill factor” is defined as theratio of the maximum power (V_(mp)×J_(mp)) divided by the short-circuitcurrent (I_(sc)) and open-circuit voltage (V_(oc)) in light currentdensity-voltage (J-V) characteristics of solar cells. The open circuitvoltage (Voc) is the maximum voltage obtainable at the load underopen-circuit conditions. The short circuit current density (J_(sc)) isthe maximum current through the load under short-circuit conditions. Thefill factor (FF), is thus defined as (V_(mp)J_(mp))/(V_(oc)J_(sc)),where J_(mp) and V_(mp) represent the current density and voltage at themaximum power point. The cell efficiency, η, is given by the equationη=(I_(sc)V_(oc)FF)/P_(in) where I_(sc) equals the short circuit current,V_(oc) equals the open circuit voltage, FF equals fill factor and P_(in)is the power of the incident solar radiation.

The fill factor and efficiency of Cells 5-8, which contain TeO₂, wassignificantly higher than Comparative Cells 1-4, which did not containTeO₂. This improvement was observed at both firing temperatures. Withoutbeing bound by theory, it is believed that the use of TeO₂ reduces theviscosity of the molten frit, thereby enabling the frit to penetrate,dissolve and/or digest the anti-reflective layer of the PV cell andimproving ohmic contact between the silver or formed metal contact andthe substrate cell.

Reference throughout this specification to “one embodiment,” “certainembodiments,” “one or more embodiments” or “an embodiment” means that aparticular feature, structure, material, or characteristic described inconnection with the embodiment is included in at least one embodiment ofthe invention. Thus, the appearances of the phrases such as “in one ormore embodiments,” “in certain embodiments,” “in one embodiment” or “inan embodiment” in various places throughout this specification are notnecessarily referring to the same embodiment of the invention.Furthermore, the particular features, structures, materials, orcharacteristics may be combined in any suitable manner in one or moreembodiments.

Although the invention herein has been described with reference toparticular embodiments, it is to be understood that these embodimentsare merely illustrative of the principles and applications of thepresent invention. It will be apparent to those skilled in the art thatvarious modifications and variations can be made to the method andapparatus of the present invention without departing from the spirit andscope of the invention. Thus, it is intended that the present inventioninclude modifications and variations that are within the scope of theappended claims and their equivalents.

1. A frit for a conductive ink for application to an anti-reflectivecoating on a semiconductor for use as a photovoltaic cell comprising:TeO₂; Bi₂O₃ in an amount in the range from about 40% by weight to about95% by weight; and SiO₂, the frit containing no intentionally-addedlead, such that upon firing at a temperature of about 750° C. to 850°C., the viscosity of the frit is reduced, enabling the frit to penetratethe anti-reflective coating to enable formation of ohmic contact betweenthe conductive ink and the semiconductor.
 2. The frit of claim 1,further comprising B₂O₃.
 3. The frit of claim 2, further comprising atleast one first oxide component selected from one or more of ZnO, Al₂O₃and combinations thereof.
 4. The frit of claim 2, further comprising atleast one second oxide component selected from one or more of Ag₂O,Sb₂O₃, GeO₂, In₂O₃, P₂O₅, V₂O₅, Nb₂O₅, Ta₂O₅ and combinations thereof.5. The frit of claim 2 further comprising at least one alkali metaloxide component selected from one or more of Na₂O, Li₂O, K₂O andcombinations thereof.
 6. The frit of claim 2 further comprising at leastone alkaline earth metal oxide component selected from one or more ofBaO, CaO, MgO, SrO and combinations thereof.
 7. The frit of claim 2,wherein the TeO₂ is present in an amount in the range from about 0.1% byweight to about 10% by weight.
 8. A conductive ink comprising asubstantially lead-free frit according to claim 1 and a conductivespecies.
 9. The conductive ink of claim 8, wherein the frit furthercomprises B₂O₃.
 10. The ink of claim 8, wherein the frit furthercomprises at least one first oxide component selected from one or moreof ZnO and Al₂O₃.
 11. The ink of claim 8, wherein the frit furthercomprises at least one second oxide component selected from one or moreof Ag₂O, Sb₂O₃, GeO₂, In₂O₃, P₂O₅, V₂O₅, Nb₂O₅, and Ta₂O₅.
 12. The inkof claim 8, wherein the frit further comprises at least one alkali metaloxide component selected from one or more of Na₂O, Li₂O, and K₂O. 13.The ink of claim 8, wherein the frit further comprises at least onealkaline earth metal oxide component selected from one or more of BaO,CaO, MgO and SrO.
 14. The ink of claim 8, wherein the TeO₂ is present inthe frit in an amount in the range from about 0.1% by weight to about10% by weight.
 15. The ink of claim 8, wherein the frit is present inamount in the range from about 1% by weight to about 5% by weight. 16.The ink of claim 8, further comprising one or more of bismuth tellurateand bismuth silicate, titania, zirconia, phosphorous compounds, andcombinations thereof.
 17. An article comprising a substrate, theconductive ink of claim 8 disposed on the substrate.
 18. The article ofclaim 17, wherein the substrate comprises a semiconductor.
 19. Thearticle of claim 18, wherein an anti-reflective layer is disposeddirectly on the substrate and the conductive ink disposed on theanti-reflective layer.
 20. A method of making a conductive ink forapplication to an anti-reflective coating on a semiconductor for use asa photovoltaic cell, the method comprising: providing a frit comprisingTeO₂, Bi₂O₃, and SiO₂, the frit containing no intentionally-added lead;and dispersing the frit in a liquid vehicle including silver particles,such that that upon firing, the frit penetrates the anti-reflectivecoating to enable formation of ohmic contact between the conductive inkand the semiconductor.